The purpose of the ice-melting and de-icing agents is to disrupt and weaken the adhesion of the ice to the surface of pavement, after which the surface can more easily be mechanically cleaned. In general, ice-melting agents are used for de-icing treatment, optionally together with added thickeners in order to increase viscosity, as well as water, surfactants and corrosion inhibitors.
The prevention of ice-formation and slipperiness is extremely important at airports in order to maintain safe conditions. Sodium chloride and other chlorides used on roads to prevent slipperiness, cannot be used at airports, since they corrode the metal parts of the planes. Thereto chlorides have a harmful effect on groundwater quality, soil, vegetation and soil microfauna. Also the use of urea, which traditionally has been used for de-icing at airports, has partly been given up due to its significant environmental load. At present acetates, liquid potassium acetate and solid sodium acetate as well as formiates, potassium formiate and sodium formiate are widely used at airports. Although these are effective in de-icing and are less detrimental to the environment, they are also heavily corrosive on metals, carbon brakes and electrical equipment of airplanes and airports. In fact ice-melting agents based on acetate and formiate have been found to cause heavy corrosion in airplane materials, including carbon brakes, metal surfaces and mating metal-metal surfaces. Further especially acetate and formiate dissolve the bitumen part of asphalt, thus causing pavement erosion and slipperiness.
Since solid and often granular ice-melting agents are easily carried away from the intended surface under the influence of air flows, liquid ice-melting agents have been found to be the most usable form of ice-melting agent. The effect of granular ice-melting agents has been found to be very local and the required amount has been found to be higher than for a liquid or wetted substance. Granular substances are however required for thicker ice in order to melt the ice down to the surface before snowploughing or brushing the surface, for example for the runway of an airport.
One more recent ice-melting agent used in liquid form is Cryotech NX360™ (Cryotech) which contains sodium acetate together with propanediol (Susterra®, Cryotech). Another ice-melting agent used in liquid form is the use of betaine as an aqueous solution for the prevention of freezing of aircrafts and runways disclosed in EP 1034231 B1. WO 2007/128878 A1 relates to the improved effect obtained by the combination of betaine and at least one other de-icing agent for de-icing treatment.
However, although betaine has been found to be a more environmental friendly alternative than urea and a non-corrosive alternative compared to the acetate and formiates used, the melting capacity of betaine as an aqueous solution has not been altogether satisfactory. Further the precipitation of betaine in concentrated aqueous solutions as well as its highly hygroscopic nature has also limited its use.
The original betaine, N,N,N-trimethylglycine, is often called glycine betaine to distinguish it from other betaines that are widely distributed in microorganisms, plants and animals. In the glycine betaine three methyl groups are bonded to the nitrogen atom of the glycine molecule.
Betaine can be obtained, for example from sugar beet by chromatographic methods. U.S. Pat. No. 5,127,957 as well as U.S. Pat. No. 4,359,430 disclose methods for the recovery of betaine from molasses and U.S. Pat. No. 5,795,398 discloses the recovery of betaine from a beet-derived sucrose containing material. U.S. Pat. No. 6,572,775 relates to a chromatographic system and U.S. Pat. No. 6,187,204 to a method for the fractionation of molasses for inter alia recovery of betaine. All methods aim for good yield as well as a high purity of the product.
Betaine has a bipolar structure and is a highly hygroscopic substance which easily turns viscous, lumpy and poorly flowable in humid conditions. In order to improve the treating properties of these hygroscopic materials in general two different approaches are used. The material may be coated with for example oil or fats which protect against humid conditions or the material may be mixed with fluidity improvers or anti-agglomeration agents which do not protect against humidity but which improve the fluidity of betaine in dry conditions. According to FR 2151076 A1 which relates to a method of improving the hygroscopicity and fluidity of different solid hygroscopic materials, such material may be treated with a powder of a calcium, magnesium, zinc or aluminium salt of a higher fatty acid.
Treating anhydrous betaine crystals is disclosed in EP 1015106 B1 which relates to arranging a hydrophobic and moisture-proof layer of calcium stearate or hydrophobic silica on the surface of the particles. The melted, hot soap is sprayed onto the surface of the betaine crystals or the soap flakes are mixed together with the betaine particles and then mixed and heated. According to EP 1015106 B1 anhydrous betaine crystals are used as an animal feed additive, in fertilizers, in cosmetic skin care products, in pharmaceutical products as well as in food.
The prior art processes for preventing ice-formation and slipperiness are not altogether satisfactory. There is a need for a non-corrosive and environmentally friendly alternative for de-icing and for preventing slipperiness. The present invention aims at satisfying that need.
It should be noted that all documents cited in this text (“herein cited documents”) as well as each document or reference cited in each of the herein-cited documents, and all manufacturer's literature, specifications, instructions, product data sheets, material data sheets, and the like, as to the products and processes mentioned in this text, are hereby expressly incorporated herein by reference.